Electromagnetic injection valves must withstand the rough operating conditions of the internal combustion engine in motor vehicles.
In particular, these injection valves are subject, on the one hand, to vibrating loads due to the periodic movements of the valve closure member back and forth and, in addition to this, to superimposed vibration from the engine. As a result, the spring which urges the valve closure member towards the valve seat frequently breaks.
The magnetic circuit of the injection valve is designed to produce a high flux density in the air gap through the valve closure member, acting as an armature, when the magnetic field is energized.
In order to maintain this flux density and the magnetic force produced thereby at a high value, the region in the vicinity of said air gap must be kept free of magnetizable materials, for which reason the springs, heretofore used thereat must be made of nonmagnetic material.
However, nonmagnetic material cannot withstand high loads as well as spring steel.